UK Tax on an invoice rebate?!

[Cmo]

I'm new to all this tax business, I have just started my own recruitment company. (To clarify, I have engaged an accountant, I just have a question now and can't contact him til next week)
I placed a candidate in a role, who left within a month (the prearranged time) and we now have to refund 50% of the invoice we were paid. The original invoice had tax, do I refund half the tax as well as half the fee???

 

[kirby]

Yes. And if you have NOT yet filed sales tax then you only pay the tax agency the net tax amount. If you already paid the full tax amount to the tax agency, apply for a refund of half the tax paid.